Now that New Horizons has completed its flyby of Pluto, the spacecraft is on a long journey to become the fifth manmade object to leave the solar system. It does so carrying some curious human artifacts: a Florida state quarter, an American flag, and one ounce of the ashes of Clyde Tombaugh, who discovered Pluto in 1930. One thing New Horizons is not carrying, however, is a message from humanity to extraterrestrial life. Jon Lomberg thinks that’s a missed opportunity. As project...